The present invention is directed to a web guidance device and to a method for guiding a moving recording medium web for a printing system, and particularly, a web guidance device for a continuous form printer device.
In the present application, a recording medium web and particularly a recording medium that has a slight to extremely slight thickness compared to a planar extent of the recording region is provided. Of course, the present invention also covers recording media that are not or not completely comprised of paper but, for example, comprise a plastic part, are completely of plastic, or have some other composition. Moreover, a recording medium provided as a roll material both with or without a margin perforation can be transported with the apparatus or the method of the present invention.
WO 99/24875 A1 (corresponding to U.S. Ser. No. 555,415) and WO 95/19929 A1 (corresponding to U.S. Pat. No. 5,685,471) disclose paper web guidance devices. These two publications are incorporated by reference into the present specification.
FIG. 2a of WO 99/24875 A1 shows a stop plate 9 of a pre-centering device 8. This stop plate 9 is secured to a runner and can therefore be displaced. The displacement occurs along a corrugated profile plate, what is referred to as a deflection seat. The guidance for an edge of the transported paper can be adjusted with the displacement of the stop plate 9. The stop plate lends the paper or, respectively, a paper web, its lateral guidance.
WO 95/19929 A1 discloses a braking device that applies a stabilization onto the paper web, so that this is no longer intended to deviate from the laterally stable position before it reaches a transfer printing region lying at a distance.
In the aforementioned Prior Art, thus the stop plate is the determining guide element for the paper web. What has now turned out to be a disadvantage of this Prior Art is that lateral damage to the paper occurs, especially given thin paper webs. Although the paper web is guided at the lateral guide plate, the mechanical stability of a lightweight, thin paper is slight, so that the forces that are introduced into the paper and occur at the edge of the paper web at the stop plate can become too high and lead to a bending or beading of the paper.
This disadvantage can be so influential that a proper paper running is no longer assured in the printer device.
It is therefore an object of the present invention to create a paper web guidance device for guiding a moving paper web such that damage to the paper web in the lateral region is dependably prevented.
According to the present invention, a web guidance device and method is provided for a continuous form printer device. The web guidance device has a deflection seat around which a recording medium web, particularly a paper web, is guided in a conveying direction. A lateral guide roller influences the recording medium web with a laterally acting force in a region of a deflection seat such that the recording medium web lies against a lateral detent. A planarly acting hold-down element is provided in a region of a lateral guide roller, the hold-down element pressing the recording medium web onto the deflection seat with a specific pressing power.
The paper web guidance device that is used in what is referred to as fan-fold printer devices that print onto a web-shaped recording medium, and comprises a deflection seat around which the web-shaped recording medium, particularly a paper web, is guided in the conveying direction. It further comprises a lateral guide roller that influences the paper web with a laterally acting force in the region of the deflection seat such that the paper web lies against a lateral detent. A planarly acting hold-down element that presses the paper web onto the deflection seat with a specific pressing power is provided in the region of the lateral guide roller.
A method for guiding a moving paper web that is adapted to the invention comprises the following steps: conveying the paper web via a deflection seat; influencing the paper web with a force in the region of the deflection seat, the force acting transversely relative to the conveying direction and being applied with a lateral guide roller that influences the paper web such that the paper web lies against a lateral detent, whereby the paper web is pressed onto the deflection seat with a specific pressing power in the region of the lateral guide roller, and whereby a planarly acting hold-down element generates the pressing power.
What can be advantageously achieved with the invention is that, even given especially thin paper webs, a buckling or beading at the lateral detent can be dependably prevented by the hold-down force that the hold-down element exerts onto the paper web in the region of the lateral guide.
As a result of being held down, the paper is prevented from escaping upward. The force that acts laterally between the lateral guide and the paper edge can be introduced into the paper without the edge beading and/or being damaged at the lateral detent.
The simple principle of the web edge control can therefore be employed despite extremely lightweight and thin papers. An escape onto, for example, the offset region with an involved web edge control via rotating frames is no longer required.
The above object, the features and advantages of the present invention can be understood better taking the following, detailed description of the preferred embodiments of the present invention into consideration and with reference to the corresponding figures.